Fetal laterality and maternal stress

This longitudinal observational study investigated whether fetuses change their hand preference with gestational age, and also examined the effects of maternal stress on lateralized fetal self-touch. Following ethical approval, fifteen healthy fetuses (8 girls and 7 boys), were scanned four times from 24-36 weeks gestation. Self-touch behaviours which resulted in a touch of the fetal face/head were coded in 60 scans for 10 minutes and analysed in terms of frequency of the fetuses using left and right hands to touch their face. The joint effects of fetal age, stress and sex on laterality were assessed. We modelled the proportion of right self-touches for each fetal scan using a generalised linear mixed model, taking account of the repeated measures design. There was substantial variability in hand preference between fetuses. However, there was no significant increase in the proportion of right-handed touches with fetal age. No sex differences in handedness were identified. However, maternally reported stress level was significantly positively related to fetal left handed self-touches (odds-ratio 0.915; p<0.0001). This longitudinal study provides important new insights into the effect of recent maternal stress on fetal predominant hand use during self-touch.